Thread breakage preventing apparatus and yarn processing machine having thread breakage preventing units

Abstract

A thread breakage preventing apparatus includes a tension relieving unit disposed on a running path of a yarn and serving to positively feed the yarn to a downstream side in a feeding amount corresponding to a tension of the yarn when the tension exceeds a preset tension. A part of the tension relieving unit is a rotational roller to be rotated at a constant rotating speed and serves to instantaneously increase and decrease the feeding amount of the yarn based on a behavior of the yarn corresponding to an increase and decrease in the tension of the yarn.

What is claimed is:  
     
         1 . A thread breakage preventing apparatus comprising: 
 a tension relieving unit disposed on a running path of a yarn and serving to positively feed the yarn to a downstream side in a feeding amount corresponding to a tension of the yarn when the tension exceeds a preset tension.    
     
     
         2 . The thread breakage preventing apparatus according to  claim 1 , 
 wherein the tension relieving unit includes a rotational roller to be rotated at a constant rotating speed, the rotational roller including a yarn feeding amount increasing and decreasing portion for instantaneously increasing and decreasing the feeding amount of the yarn based on a behavior of the yarn corresponding to an increase and decrease in the tension of the yarn.    
     
     
         3 . The thread breakage preventing apparatus according to  claim 2 , 
 wherein the yarn feeding amount increasing and decreasing portion includes a taking and feeding structure for leading out the yarn against a fluctuation in the tension when an abnormal tension of the yarn is generated and for instantaneously feeding the yarn in a necessary feeding amount to a downstream side.    
     
     
         4 . The thread breakage preventing apparatus according to  claim 1 , 
 wherein the tension relieving unit includes a rotational roller contacting the yarn by pressure, and a pressure contact force of the yarn against the rotational roller is increased by gripping the yarn when a tension of the yarn exceeds a predetermined value.    
     
     
         5 . The thread breakage preventing apparatus according to  claim 1 , 
 wherein the tension relieving unit includes a rotational roller and a guide roller, and the yarn is laid like a zigzag over the rotational roller and the guide roller.    
     
     
         6 . A yarn processing machine comprising: 
 a thread feeding portion;    a tension relieving unit disposed on a running path of a yarn and serving to positively feed the yarn to a downstream side in a feeding amount corresponding to a tension of the yarn when the tension exceeds a preset tension; and    a yarn processing portion,    wherein the tension relieving unit is provided on the running path between the thread feeding portion and the yarn processing portion.    
     
     
         7 . The yarn processing machine according to  claim 6 , wherein the yarn processing portion is a twisting spindle.  
     
     
         8 . A thread plying machine comprising: 
 a thread feeding portion;    a tension relieving unit disposed on a running path of a yarn and serving to positively feed the yarn to a downstream side in a feeding amount corresponding to a tension of the yarn when the tension exceeds a preset tension; and    a yarn processing portion; and    a feed roller; and    a twine winding portion,    wherein the tension relieving unit is provided on the running path between the thread feeding portion and the yarn processing portion, and    wherein the feed roller is provided between the yarn processing portion and the twine winding portion and serving to overfeed a twine to the twine winding portion.    
     
     
         9 . The thread plying machine according to  claim 8 , 
 wherein the tension relieving unit is a rotational roller to be rotated at a predetermined rotating speed, and the feed roller has the same structure as a structure of the rotational roller, and the rotational roller and the feed roller are supported on an identical rotating shaft.